This application claims the benefit of Korean Application No. 2002-8786, filed Feb. 19, 2002, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates in general to a plasma display apparatus which displays images thereon by use of an electric discharge, and more particularly, to a plasma display panel (hereinafter, a xe2x80x9cPDPxe2x80x9d) having a circuit to recover reactive power.
2. Description of the Related Art
A PDP is an apparatus that allows pictures to be displayed thereon using a gas discharge. Depending upon types of methods used to drive the PDP, the PDP is largely categorized into a direct current (DC) type PDP, which performs a facing discharge, and an alternating current (AC) type PDP, which performs a surface discharge. The AC type PDP is more advantageous since it has a lower power consumption and a longer lifetime in comparison with the DC type. For this reason, the AC type PDP has lately attracted considerable attention.
The PDP using the AC driving type applies an alternating current (AC) voltage between electrodes insulated with a dielectric layer, and performs a discharge every half-cycle of the AC voltage. The AC type PDP displays a picture mainly in a sub-field method. In the sub-field method, since the power consumption used to charge and discharge of the PDP panel during a sustain of the discharge is very large, a circuit is used in a driving device of the PDP to recover reactive power.
Generally, the reactive power recovering circuit includes a scanning/sustaining electrode unit that drives cells connected to a Y-electrode (hereinafter, xe2x80x9cY-electrode unit driving cellxe2x80x9d 20) and a common electrode unit that drives cells commonly connected to a plurality of X-electrodes (hereinafter, xe2x80x9cX-electrode unit driving cellxe2x80x9d 30). As shown in FIG. 4, adjacent pairs of the Y-electrodes and the X-electrodes are arrayed in sustaining electrode pairs. The sustaining electrode pairs perform a surface discharge using sustain pulses generated in the Y-electrode unit driving cell 20 and the X-electrode unit driving cell 30. By these pulses, a brightness of the picture displayed on a screen is sustained. A panel capacitor 39 indicates an electrostatic capacity formed between the Y-electrode and the X-electrode in the panel in an equivalent manner.
The Y-electrode unit driving cell 20 includes first and second switches 31 and 33 connected in series between an outside sustaining voltage supply source (Vcc) and a ground (i.e., the Y-electrode), an outside capacitor 43a provided in parallel relative to the second switch 33, third and fourth switches 35 and 37 provided between the outside capacitor 43a and a first node n1, and a coil 41 connected between the first node n1 and a second node n2. The X-electrode unit driving cell 20 is constructed symmetrically to the Y-electrode unit driving cell 20, with the panel capacitor 39 being in the center therebetween. The X-electrode unit driving cell 30 includes fifth and sixth switches Xs and Xg corresponding to the first and second switches 31 and 33, seventh and eighth switches Xr and Xf corresponding to the third and fourth switches 35 and 37, a coil Lx, and an outside capacitor 43b. 
Hereinbelow, the operation of the reactive power recovering circuit will be described, focusing on the Y-electrode unit driving cell 20. The panel capacitor 39 is charged with voltage according to the on/off states of each switch 31, 33, 35, 37, Xs, Xg, Xr, Xf of the X and Y-electrode unit driving cells 20 and 30. The voltage charged in the panel capacitor 39 is discharged at the period when the second switch 33 is turned on. If the fourth switch 37 is simultaneously turned on during the discharge of the panel capacitor 39, the electric current flows into the outside capacitor 43a, thereby allowing energy to be absorbed thereinto. Then, if the third switch 35 is turned on, the energy absorbed into the outside capacitor 43a is recovered by passing through the coil 41, and the panel capacitor 39 is charged again with the energy. Thereafter, the energy is used in a next switching process.
At this time, to supplement insufficient voltage of the panel capacitor 39, the first switch 31 is turned on. The voltage charged in the panel capacitor 39 is discharged depending on the on/off state of each switch Xs, Xg, Xr, Xf within the X-electrode unit driving cell 30, as in the switching process of the Y-electrode unit driving cell 20. Through these processes described above, the X-electrode unit driving cell 30 alternately charges and discharges the panel capacitor 39 with the Y-electrode unit driving cell 20. As a result, the sustaining discharge is available by charging/discharging the panel capacitor 39 by use of the outside capacitors 43a, 43b, which respectively function as a voltage source.
However, in the conventional reactive power recovering circuit, the construction of the circuit for recovering the energy itself has been very complicated. In addition, the amount of power consumed by each switching device and each diode, to which a plurality of switching devices and a diode to prevent a reverse flow are connected in series, has been large.
The present invention has been made keeping in mind the above and other problems and shortcomings, and an object of the present invention is to provide a plasma display panel having a reactive power recovering circuit simplified in structure, wherein power consumption is reduced, and a method of controlling the same.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
This and other objects of the present invention may be achieved by providing a plasma display panel according to an embodiment of the invention comprising a power supply source to provide a supply voltage, first and second discharge electrodes to perform a surface discharge with the supply voltage from the power supply source, a panel capacitor whose opposite ends are connected to the respective discharge electrodes, the panel capacitor being discharged by supplying a charge voltage to either of the first discharge electrode or the second discharge electrode, a plurality of switches to turn on or off a connection of the panel capacitor connected to the respective discharge electrodes and the power supply source, an inductor provided between the panel capacitor and one of the first and second discharge electrodes, the inductor being charged by a discharge current discharged from the panel capacitor and to inductively store the charge voltage to be recovered for use by the panel capacitor, and a controller to control the switches so as to allow the charge voltage of the panel capacitor to be alternately supplied to the respective discharge electrode.
According to an aspect of the invention, one of the switches comprises a power connecting switch to turn on or off the supply voltage from the power supply source to the panel capacitor, and another one of the switches comprises a ground connecting switch to turn on or off a connection of the panel capacitor with one of the first and second discharge electrodes.
According to another aspect of the invention, the plasma display panel further comprises a resistor connected in series to the power connecting switch in order to reduce an overshoot voltage.
According to yet another aspect of the invention, the switches include field effective transistors (FETs).
According to another embodiment of the present invention, a method of recovering a reactive power of a plasma display panel, which includes a power supply source, a panel capacitor charged with a supply voltage from the power supply source, first and second discharge electrodes performing a surface discharge according to charge/discharge of the panel capacitor, switches to charge/discharge the panel capacitor, and an inductor connected in series to the panel capacitor, the method comprising charging the panel capacitor, discharging the panel capacitor and charging the inductor with a discharged current, forming a first electric current path from the inductor to the panel capacitor and charging the panel capacitor with a charged energy of the inductor, and forming a second electric current path in a reverse direction of the first electric current path and discharging the panel capacitor.
According to a further aspect of the invention, the charging the panel capacitor by the inductor further comprises supplementing insufficient voltage of the panel capacitor with the voltage supplied from the power supply source.
According to a further aspect of the invention, one of the switches includes a power connecting switch to turn on or off a voltage supplied from the power supply source to the panel capacitor, and another of the switches includes a ground connecting switch to turn on or off a connection of the panel capacitor with one of the first and second discharge electrodes.
According to a yet further aspect of the invention, a resistor is connected in series to the power connecting switch, thereby reducing overshoot voltage.
According to a still further aspect of the invention, the switches include field effective transistors (FETs).